Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/24/2007
Publication Date: 12/1/2007
Citation: Wood, B.W. 2007. Correction of zinc deficiency in pecan by soil banding. HortScience. 42(7):1554-1558. Interpretive Summary: The managing of pecan trees to ensure that zinc needs are satisfied is an expensive annual cost to producers. An improved method is needed that reduces the cost of zinc management. A new approach was developed utilizing ground banded zinc to provide long-term control of tree zinc nutrition, and demonstrated that the relatively inexpensive oxide form of zinc is as good as is the more expensive sulfate form. The strategy offers a long-term and less costly approach to zinc management in acidic soil environments.
Technical Abstract: Zinc (Zn) deficiency is common in commercial pecan [Carya illinoinensis (Wangenh.) C. Koch] orchards. Correction via multiple annual foliar spray applications is expensive, but effective in eliminating Zn deficiency. Correction by soil application is also expensive and is usually impractical or non-effective. There is need for more economical and long lasting methods for satisfying tree Zn nutritional needs. It is reported here that tree foliar Zn needs (i.e. >50 ug.g-1 dw) are potentially met via one-time “banding” of Zn sulfate (ZnSO4.7H2O) or Zn oxide (ZnO) onto orchards floors. Zinc needs of four-year-old ‘Desirable’ trees growing on acidic soil were satisfied over a four-year period by a single banded soil application of either Zn sulfate or Zn oxide over underground drip-irrigation lines at a Zn rate of 2,112 g Zn per tree (giving foliar Zn concentrations of 60–115 ug.g-1 dw). Rates of Zn at 264-1,056 g per tree are occasionally efficacious, but rates < 264 g Zn per tree (0, 33, 66, and 132) were always ineffective for meeting a leaf sufficiency threshold of 50 ug.g-1 dw. Sulfate and oxide Zn-forms were equally effective in meeting tree Zn needs. Foliar Zn concentrations increased quadratically with increasing soil banded Zn treatments; however, foliar Zn concentrations did not necessarily increase over the four-year period within each Zn-rate treatment. Increasing amounts of banded Zn per tree also increased foliar Mn concentration (from '150 - 269 ug.g-1 dw) of treated trees the fourth year post-treatment, but did not affect foliar concentration of other key micronutrients (i.e., Fe, Co, Cu, or Ni). This fertilization strategy offers an efficacious alternative to annual foliar Zn sprays for orchards established on acidic soils, and provides a means of ensuring rapid and long-term Zn absorption via soil application. The approach indicates that soil banding of Zn on certain acidic soils can satisfy the nutritional needs of pecan trees for several years after a single application.